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Classification of Matter
Mixtures, elements, compounds
Scientists like to classify things. One way that scientists classify matter is
by its composition. Ultimately, all matter can be classified as
mixtures, elements and compounds.
Why isn’t it a good idea to classify matter by its phases?
Because one kind of substance can exist in more than one phase – such as H20. And matter changes phases rather easily.
Why isn’t matter classified according to its physical characteristics, such as color?
Scientists wouldn’t find it very useful to group gold, sunflowers, and the sun together.
Composition of Matter Flowchart
MATTER
Can it be physically separated?
Homogeneous Mixture
(solution)
Heterogeneous Mixture Compound Element
MIXTURE PURE SUBSTANCE
yes no
Can it be chemically decomposed?
noyesIs the composition uniform?
noyes
Classifying Matter by Composition
Mixtures- are a blend of two or more kinds of matter, each of which retains its own identity and properties. A mixture is mixed together physically. Variable composition, often expressed
by a percent composition by mass or volume (Ex. 5% salt and 95% water
Classifying Matter by Composition
1. Homogeneous – matter with a uniform composition. They are also called solutions. Ex. Salt water and Kool –aid
2. Heterogeneous - matter without a uniform composition
Homogeneous Mixtures
A mixture that appears to be the same throughout.
It is “well mixed.” The particles that make up the mixture
are very small and not easily recognizable.
Examples of homogeneous mixtures
Milk, toothpaste, and mayonnaise are homogeneousmixtures. They are also colloids.
Colloids
In a colloid the particles are mixed together but not dissolved.
The particles are relatively large and are kept permanently suspended.
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Colloids
A colloid will not separate upon standing.
The particles are constantly colliding, and this allows a colloid to scatter light – thus colloids often seem cloudy.
Solutions A solution is a type of homogeneous
mixture formed when one substance dissolves in another.
It is the best mixed of all mixtures. A solution always has a substance that is
dissolved and a substance that does the dissolving.
The substance that is dissolved is the solute and the substance that does the dissolving is the solvent.
Ocean water is a solution
Water as a solvent
Many liquid solutions contain water as the solvent.
Ocean water is basically a water solution that contains many salts.
Body fluids are also water solutions.
Types of solutions
Gas Gas Air (oxygen in nitrogen)
Gas Liquid Soda water (carbon dioxide in water)
Solid Liquid Ocean water (salt in water)
Solute Solvent Example
Solid Solid Gold jewelry (copper in gold)
Metals dissolved in metals are called
alloys.
Air is a solution of oxygen and other gases dissolved in nitrogen
Alloys
Brass is an alloy of copperand zinc.
Stainless steel is a mixtureof iron and chromium.
Classifying Matter by Composition
A heterogeneous mixture is not the same throughout (not uniform).Considered the “least mixed.”Does not appear to be the same throughout.Particles are large enough to be seen and to
be separated from the mixture.
Examples of heterogeneous mixtures Sand and pebbles, gravel, soil, rocks Oil and water, salad, M & M’s, Chocolate cookies.
Granite is a heterogeneous mixture.
Separating MixturesMixtures are separated by their
physical properties. Primary methods of separatingmixtures are:filtrationdistillationcentrifugechromatography
Separating Mixtures
Filtration is a method used to separate the components of mixtures that contain an insoluble solid and a liquid. Example: sand and water
Separating Mixtures
Distillation is a method of separating substances in a mixture by evaporation of a liquid and subsequent condensation of its vapor. Example: desalination of salt water
Separating Mixtures
Centrifuge Used to separate solid-liquid
mixtures such as those in blood. The centrifuge spins rapidly and causes the solid to settle to the bottom.
Ex. Separating blood
Separating Mixtures
Chromatography is a method of separating mixtures that uses a stationary phase and a mobile phase. Paper chromatography can be used to separate pigments because they move at different rates on the paper.
Composition of Matter Flowchart
MATTER
Can it be physically separated?
Homogeneous Mixture
(solution)
Heterogeneous Mixture Compound Element
MIXTURE PURE SUBSTANCE
yes no
Can it be chemically decomposed?
noyesIs the composition uniform?
noyes
Classifying Matter by Composition
Pure Substances- A pure type of matter that does not vary from sample to sample. Includes elements and compounds
Classifying Matter by Composition1-Elements- simplest kind of matter, made of one type of atom An atom is the smallest unit of an element
that maintains the properties of that element.
Cannot be broken down into simpler substances by ordinary chemical means
Ex. gold, copper, oxygen (on the periodic table)
Classifying Matter by Composition
2-Compounds – matter composed of the atoms of two or more elements chemically bonded Compounds can be broken down by
chemical methods When they are broken down, the
components have completely different properties than the compound.
Ex. Sugar, salt, water, carbon dioxide
Compounds
Compounds are also pure substances.
But compounds are made from more than one element.
Water is a compound. Water can be broken
down into simpler substances – hydrogen and oxygen.
Classify Itcopper wire, aluminum foil
Classify It Examples:
Magnesium-
Pizza -
Calcium chloride
Orange juice
Club soda
element
hetero. mixture
compound
hetero. mixture
Homo. (solution)
States of matter Solid- matter that can not flow and has
definite volume and shape Liquid- definite volume but no definite
shape and can flow Gas- a substance without definite
volume or shape and can flow. Plasma- a substance that is similar to a
gas, but loses electrons due to its high temperature
States of Matter
Solid
Liquid
Gas
Definite Volume?
YES
YES
NO
Definite Shape?
YES
NO
NO
Particle position and movement
Packed tightly, vibrate about fixed pt
Close together, can move past each other - flow
Far apart, move rapidly - flow